1. Field of the Invention
The invention relates to presses for hydrostatic extrusion with a die support and particularly to sealing such presses at the die end.
In presses for hydrostatic extrusion very high pressure levels are used; usually the working pressure is between 10 and 20 kbar. At this high pressure a reliable seal must be achieved between the inner wall of a press cylinder and a die or a die support and between the inner wall of the cylinder and a punch or a piston projecting into the cylinder, said punch or piston, when it is inserted into the cylinder, producing the high extrusion pressure in a pressure medium which is enclosed in a pressure chamber formed of the cylinder, the die and the piston. A billet to be extruded is located in the pressure chamber and is pressed out through the die under the effect of a pressure medium. On raising the pressure from atmospheric level the extrusion level, the inner diameter of the cylinder increases by 0.5 to 1%, which requires a seal to prevent pressure medium from flowing out through a gap between the cylindrical wall and the piston and the die, respectively, which expands upon a pressure increase. Any leakage at the high pressures mentioned may involve severe damage to the die or the die support, which requires an exchange of these expensive parts.